Diabetes affects some 20 million people in the U.S. The World Health Organization expects the global diabetics population to rise from 130 million to 350 million by 2025. Diabetes therapy based on transplanted islets or insulin-secreting Beta cells offers substantial advantages over conventional treatments. We plan to develop Magnetic Resonance Imaging (MRI) probes for in vivo non-invasive monitoring of the disposition, mass and viability of transplanted insulin secreting tissue. The availability of quantitative in vivo MRI methods for islet and Beta-cell mass would provide benefits for early diagnosis of the disease and for islet transplantation research aimed at improving current protocols methodologies. It would also establish islet transplantation as a realistic treatment option for patients requiring insulin replacement therapy. Our plan is to evaluate the feasibility of using novel Beta-cell specific MRI probes to monitor in vivo the disposition, mass and viability of large volumes of transplanted islets or Beta-cells. The new probes will be based on MRI imagable probes that display specificity towards membrane components of pancreatic Beta cell mass. The initial phase will establish the in vitro feasibility of the new diagnostic probes, leading up to subsequent in vivo studies. The development of imaging techniques and reagents that lead to non-invasive in vivo assessment of Beta-cell mass may have a significant impact in managing pancreas and/or islet transplantation, in the understanding of the pathogenesis in islet engraftment, and for assessing the efficacy of modulations in type 1 diabetes therapy.